Konferenz der Datenschutzbeauftragten des Bundes und der Länder

Dokumentation

Konferenz der Datenschutzbeauftragten des Bundes und der L?nder Entschlie?ung vom 16. April 2009     

A first or dominant immunization. I. Suppression of simultaneous cytolytic T cell responses to unrelated alloantigens

A first or dominant immunization with one antigen markedly inhibited specific cytolytic T lymphocyte (CTL) responses to a second unrelated alloantigen without suppressing antibody responses to other antigens. Suppression was induced rapidly, became systemic, and could be transferred passively with only serum. Suppression did not result from elimination of cells capable of responding to the second antigen. The mechanisms responsible for this "priority of the first response" may be the same that help protect the fetus during pregnancy, promote renal allograft survival after multiple blood transfusions, and prevent effective CTL-mediated immunity to variants of tumor cells or infectious agents that arise during tumor progression or chronic infections.     

Multifractal characterization of unworn hydrogel contact lens surfaces

Purpose: The aim of this work was to estimate the multifractal spectra of 3D surface roughness for unworn hydrogel contact lenses (CL), obtained with atomic force microscopy (AFM) analysis. Materials and methods: Contact lenses made from vifilcon A (Focus® Monthly Toric Visitint® model, CIBA Vision Corp.) were investigated. CL surface roughness was studied by AFM in tapping‐mode™, in an aqueous environment, on square areas ranging from 1 to 4 μm². A detailed methodology for CL surface multifractal characterization, which may be applied for AFM data, was presented. Results: The CL surface roughness revealed multifractal geometry at various magnifications. The generalized dimension D_q and the singularity spectrum f(α) provided quantitative values that characterize the local scale properties of CL surface geometry at nanometer scale. Conclusions: Multifractal analysis provides different yet complementary information to that offered by traditional surface statistical parameters. POLYM. ENG. SCI., 54:1066–1080, 2014. © 2013 Society of Plastics Engineers     

The effect of twin plane spacing on the deformation of copper containing a high density of growth twins

In-situ tensile straining in a transmission electron microscope was used to investigate the role of twin plane spacing on the deformation and fracture mechanism of pure copper containing a high density of nanoscale growth twins. Real-time and post-mortem observations clearly reveal that twin plane spacing plays a key role in determining the operative deformation mechanism and therefore the subsequent crack propagation path. The deformation mechanism transition, which results from changes in the twin plane spacing, has implications for interpreting the unusual mechanical behavior of the copper with a high density of nanoscale growth twins.     

Characteristic dimensions and the micro-mechanisms of fracture and fatigue in `nano' and `bio' materials

The behavior of small-volume (so-called `nano') structures, where size-scales are comparable with microstructural dimensions, and biological/bio-implantable materials, which invariably display a hierarchy of structural dimensions, is currently much in vogue in materials science. One aspect of this field, which to date has received only limited attention, is the fracture and fatigue properties of these materials. In this paper, we examine two topics in this area, namely the premature fatigue failure of silicon-based micron-scale structures for microelectromechanical systems (MEMS), and the fracture properties of mineralized tissue, specifically human bone.     

In situ TEM nanoindentation and dislocation-grain boundary interactions: a tribute to David Brandon

As a tribute to the scientific work of Professor David Brandon, this paper delineates the possibilities of utilizing in situ transmission electron microscopy to unravel dislocation-grain boundary interactions. In particular, we have focused on the deformation characteristics of Al–Mg films. To this end, in situ nanoindentation experiments have been conducted in TEM on ultrafine-grained Al and Al–Mg films with varying Mg contents. The observed propagation of dislocations is markedly different between Al and Al–Mg films, i.e. the presence of solute Mg results in solute drag, evidenced by a jerky-type dislocation motion with a mean jump distance that compares well to earlier theoretical and experimental results. It is proposed that this solute drag accounts for the difference between the load-controlled indentation responses of Al and Al–Mg alloys. In contrast to Al–Mg alloys, several yield excursions are observed during initial indentation of pure Al, which are commonly attributed to the collective motion of dislocations nucleated under the indenter. Displacement-controlled indentation does not result in a qualitative difference between Al and Al–Mg, which can be explained by the specific feedback characteristics providing a more sensitive detection of plastic instabilities and allowing the natural process of load relaxation to occur. The in situ indentation measurements confirm grain boundary motion as an important deformation mechanism in ultrafine-grained Al when it is subjected to a highly inhomogeneous stress field as produced by a Berkovich indenter. It is found that solute Mg effectively pins high-angle grain boundaries during such deformation. The mobility of low-angle boundaries is not affected by the presence of Mg.Special title: Advanced Materials and Characterization: Proceedings of the Brandon Symposium; Guest Editors: Wayne D. Kaplan and Srinivasa Ranganathan     

Advanced mixed oxide fuel assemblies with higher plutonium contents for pressurized water reactors

Optimizing fuel cycle costs by increasing the final burnup leads to reduced generation of plutonium. Under properly defined boundary conditions thermal recycling in mixed oxide (MOX) fuel assemblies (FAs) reduces further the amount of plutonium which has to be disposed of in final storage. Increasing the final burnup requires higher initial enrichments of uranium fuel to be matched by an advanced design of MOX FAs with higher plutonium contents. The neutronic design of these MOX FAs has to consider the licensing status of nuclear power plants concerning the use of MOX fuel. The Siemens Nuclear Fuel Cycle Division, with more than 20 years' experience in the production of MOX fuel, has designed several advanced MOX FAs of different types (14 × 14 to 16 × 16) with fissile plutonium contents up to 4.60 w/o.     

Multifractal detection of overlaps based on a stereometric analysis of a fracture surface: Assumptions

The paper presents theoretical assumptions of an analysis of stereometric files for the purpose of the detection of the occurrence of overlaps. The measured data of a fracture surface were obtained using a profilographometer. An algorithm has been developed based on the probability of the occurrence of maximum Euclidean distances in the investigated areas of the stereometric image. An analysis of real fractures and overlaps [Stach S, Roskosz S, Cwajna J, Cybo J. Graphic visualization of overlaps occurring in sintered carbides' fractures, Materials Characterization 2006-this issue. doi:10.1016/j.matchar.2006.01.007. [1]] has corroborated a high effectiveness of multifractal detection.     

Characterization of the acidity of faujasite- and pentasil-zeolites by calorimetric measurements of the ammonia chemisorption

Using the methods of calorimetric and isosteric measurements of the ammonia adsorption, it is found that the lower limit of the heat of chemisorption in H-Y- and H-ZSM-5-zeolites is 60 kJ/mol. Dealumination of the Y- and ZSM-5-zeolites changes the total number of the acid sites as well as the strength and the strength distribution of the Brönsted sites. Within a margin of error of ± 10 %, there is a coincidence of the number of measured and calculated Brönsted sites (from the Al-content of the frame-work) in H-Y- zeolites.     

Deep levels of platinum in silicon

Platinum has received renewed attention of late from device engineers as a means of lifetime-control in silicon. The energy levels assigned to platinum are not well defined, however, and ambiguities exist in the literature. In this work platinum was introduced into n- and p-type silicon and the energy levels and concentrations studied by thermally stimulated current and capacitance techniques. p]Schottky barrier diodes were used to study electron emission from two levels found in the upper half of the band gap. The use of Schottky barriers eliminated the problem of process-induced defect introduced by high concentration p⁺ diffusions. Phosphorus-diffused n⁺ - p diodes were used to study hole emission from three levels found in the lower half of the band gap. Platinum concentration versus distance profiles were obtained from thermally stimulated capacitance measurements. Experimental results indicate that the platinum concentration follows the boron concentration distribution near the junction in p-type silicon.